The Bicycle and Motorcycle Dynamics (BMD) Conference is held every three years. The first conference was held in Delft, The Netherlands in 2010. The aim of this symposium is to bring together leading scientists and researchers in the field of bicycle and motorcycle dynamics and control, in a broad sense. Topics include but are not limited to: single track vehicles (e.g. bicycles, motorcycles, scooters), narrow track and tilting vehicles, unicycles, dicycles (e.g. Segways and hoverboards), modeling, kinematics and dynamics, control, human control, rider properties, handling qualities, tires, experiments, aerodynamics, simulators, nonholonomic dynamics, robot riders, path following. For an open sharing of information, the meeting is organized to provide as much interaction between participants as possible. The format is informal and fluid, with a single track of presentations and extensive time scheduled for interaction, and the forming and sharing of ideas. In addition, there will be room for poster presentations.
Optimizing the performance of racing motorcycles is a central goal for competition teams. The necessity to ensure driver stability and a good level of grip in the widest possible range of riding conditions makes it necessary for tires to work in the right temperature window, capable of ensuring the highest interaction force between tire and road. Specifically, the internal temperature of the tire is a parameter that can be difficult to measure and control but has a significant impact on motorcycle performance and, also, on driver stability. Deepening knowledge of internal tire temperature in racing motorcycles can improve performance optimization on the track and finding the right motorcycle setup. In this work, a physical thermal model is adopted for an activity concerning the development of a moto-student vehicle, to predict the racing motorcycle setup allowing the tire to work in a thermal window that optimizes grip and maximizes tire life. More in detail, a focus has been placed on the effects of the motorcycle’s wheelbase and pivot height variations on internal tire temperatures. Indeed, the stability and handling of the vehicle are highly dependent on the geometric properties of the chassis. Several values of such quantities have been tested in a properly implemented vehicle model developed in the “VI-BikeRealTime” environment, validated by outdoor tests, able to provide forces acting on the tires, slip indices, and speeds, needed by the thermal model as inputs. Through the analysis of the internal temperatures calculated by the model, reached by the various layers of the tire, it has been possible to investigate which of the simulated conditions cause a too-fast thermal activation of the tire and which of them can avoid overheating and underheating phenomena. Lately, this research has delved into the correlation between motorcycle riders' paths and temperature fluctuations with the aim of comprehending how minor alterations in routine maneuvers may influence tire energy activation, particularly in the context of racing and qualifying conditions.
Understanding and mastering handling quality is a critical concern for bicycle designers, as it directly impacts safety, comfort, and performance. However, this aspect has received limited attention to date. Existing literature offers experimental handling quality indicators based on bicycle kinematics, but their validity has yet to be established. This study aims to assess the predictive power of these indicators using experimental data derived from subjective assessments of handling quality. These data, obtained from a protocol involving 20 participants and 2 bicycles, enabled testing 39 experimental indicators. The results indicate that certain vehicle kinematic quantities are indeed correlated with the perception of handling quality but with low predictive power. Indicators based on handlebar movement are the most effective in explaining the sensation of handling quality. These indicators perform particularly well at low speeds, where physical and cognitive workload are associated with the quantity of control actions on the handlebars.
To develop advanced motorcycle assistance systems, the focus is shifting towards the rider's abilities. A model in (Scherer et al. 2022) predicts motorcycle dynamics influenced by riders without specific rider or vehicle parameters. It employs mathematical functions to describe speed and roll angle changes, revealing differences among riders. Unlike previous stochastic approaches, this model allows clear interpretation of measurement data with rider-specific parameters like correction amplitudes and trends, aiding critical maneuver identification. The paper investigates applying this rider model to real traffic data. For this purpose, three riders (two experienced frequent riders and one inexperienced infrequent rider) on two different vehicles (Honda CBF 1000 and BMW K1200R Sport) were recorded and examined on a sample basis using a validated low-cost measurement technique with a total amount of n = 40 measurements. Taking into account evaluation curves suitable for proving the methodology, two consecutive country road curves were selected with a respective change in direction (equivalent to a yaw angle change of the vehicle between entering and exiting the curve) of approx. 180°. These were each driven through 5 times by all three riders under constant conditions in good, summer weather and road conditions. In addition, one of the riders drove through them in wintry and less than optimal road conditions at the beginning of the season. Initial findings assess the model's transferability to real traffic. The investigation results show its applicability, with rider-specific riding styles and parameterization functions, as well as the need to repeat the study with a large number of samples. The model accurately predicts future positions, with over 85% of maneuvers having less than a 2% lateral deviation. This demonstrates applicability under real conditions, confirming its efficacy beyond the closed terrain test in (Scherer et. al., 2022). In the future, this model will enable rider-dependent trajectory predictions with uncertainty intervals in real traffic situations.
We previously presented a narrow-track tilting tricycle with a variable stability mechanism integrated between the swing arms that support a pair of rear wheels, in the so-called “delta” configuration, and with recumbent seating. We now examine adopting that variable stability mechanism to work on a tricycle with a split-parallelogram linkage between a pair of front wheels, in the so-called “tadpole” configuration, and with upright seating. It was fairly straightforward to allow for tilting by replacing the front wheel and fork with a split parallelogram comprising two paired A-arms and kingpins, controlling the motion of the two halves with a bell crank and two tie rods, and then varying the handling of the vehicle by moving the connection point of the tie rods on the bell crank, just as we did with the swing arms of the previous vehicle. We have also separated the two tasks of positioning the tie rod ends on the bell crank and enforcing symmetry of the tie rods. The former does not require much force and can be easily implemented with Bowden cables, but the latter does require large forces and is better implemented with a local rigid-bar linkage. Implementing decent Ackermann steering geometry, allowing for both large tilt and steer angles, and decoupling tilting from steering, however, proved to be quite a challenge, at least while we attempted to implement it with bar linkages. Fortunately, we discovered a 2006 paper by Prof Drstvenšek et al. describing a Bowden cable and cam system that looked promising. Finally, the resulting vehicle handles very nicely. When in “full bicycle” mode, it handles quite similar to the original bicycle that we had converted into the tricycle. When in “rigid tricycle” mode, it keeps the rider upright when stationary or when riding at a walking pace. In between these two extremes, it handles even better than the original bicycle in a slalom course and when slowly following a straight line.
Bicycle mobility has become increasingly popular as a sustainable and healthy means of transportation. Bicycles are not only a cost-effective transportation mode but also help reduce traffic congestion and air pollution. However, the efficiency and safety of bicycling largely depend on the optimization of bicycle components, such as the tires. The importance of bike tire optimization cannot be underestimated as it can affect both bicycle dynamics and bicycle performance. Due to the lack of multi-physical mathematical models able to analyze and reproduce complex tire/road contact phenomena, useful to predict the wide range of working conditions, this research aims to the development of a bicycle tire thermal model. The main outcome is to provide the full temperature local distribution inside the tire’s inner rubber layers and the inflation chamber. Such kind of information plays a fundamental role in the definition of the optimal adherence conditions, for both safety and performance maximization, and as an indicator of the proper tire design for various applications, each requiring specific heat generation and management. The experimental validation has been carried out thanks to an innovative test-rig developed at Politecnico di Milano. It is known as VetyT (acronym of Velo Tyre Testing), and it complies with the standard ISO 9001-2015. It has been specifically instrumented for the activity, acquiring the external tire temperatures to be compared with the respective simulated ones, under various workingconditions.
Statistics show, that bicycles become more and more popular as transportation method, e.g. 25% increase in Germany between 2019 and 2021 (Sinus, 2021). To ensure the safety of bicycle riders as vulnerable road users (VRUs), analysing critical traffic situations is essential (Wendel, 2020). To be able to explore such situations in a safe environment, a bicycle simulator was built at DLR that can be used stand-alone or in combination with other simulators in order to integrate other traffic participants such as pedestrians or car drivers (Fischer et al., 2022; Martinez Garcia, 2021). This work describes the development of the simulator with the goal of creating a realistic and therefore immersive cycling experience (Jacobi, 2022; Janssen, 2022). A detailed description of the implementation of the recent improvements is provided as well as an objective evaluation for validation of the simulator.
A 2-Skate, short for a Two-Inline-Ice-Skates-Single-Track-Vehicle, was built to show that without wheels, gyroscopic effects, fork angle, trail and power-to-the-wheels, a person could ride it. But the rider might have been a circus acrobat that can also sit backwards on his bicycle handlebar, and pedal while juggling and turning around in a circle. So this current study aimed at determining if normal persons can ride the 2-Skate with confidence, with the same phase lag between torso and vehicle leaning while slaloming, and the same torso and vehicle lean angles in steady state curves as predicted. A protocol was designed and 13 independent riders tested the 2-Skates. On their first trial, with the exception of a 79 year old, they could all ride it and go slaloming. Three did the phase lag and lean angle tests and obtained similar results, confirming the prediction of the Torso-Arms-Handlebar Steering Theory first presented by Ethier (1974), with differential non-holonomic and servomechanism system equations, and further explained on the web with access to recently revised equations. This confirmation (a) sheds light on how bicycles are steered, (b) clarifies that Countersteering is done automatically at low speeds, (c) supports and clarifies the way mountain bike steering is taught, (d) suggests a slight modification of the way motorcycle Countersteering is taught, (e) can be used to develop a different approach to 2-Wheeler simulators, (f) and can renew interest for motorcycles with seat belts and protective structure like the BMW-C1, and the closed-cabin electric motorcycles like the ultra-low drag and award winning Peraves e-Tracer.
This contribution presents an analysis of the vertical tyre stiffness of 20” bicycle tyres as usually mounted on bicycle carriers for the transport of children. The current research contributes to the science on bicycle comfort with the focus on the next generation cyclists. Two different methods to measure vertical or radial tyre stiffness of bicycle tyres are presented – a dynamic approach on a dynamic press and a static approach. Parameters modified are tyre inflation pressure and vertical load in the static experiment. In the dynamic experiment additionally dynamic load and frequency are varied. The dynamic experiments are performed on two different tyres. The same tyres are also used for the static experiments and completed with a third tyre, which is a clincher version of the narrow foldable tyre. The tyres are made for 406mm rim diameter as usually for bicycle carriers since the comfort of children in bicycle transportation is the larger scope behind the experiments. The main findings are as follows: • The stiffness of the tyres is in a range of 31 N / mm to 147 N / mm. It must be considered that values below 50 N /mm are related to extremely low inflation pressure that probably do not work reliably because the rim will puncture the tube. • Tyre inflation pressure is the main factor that controls the vertical stiffness. • Type of tyre (balloon vs. narrow tyre) hardly affects the stiffness. • The dynamic stiffness at 1 Hz is slightly higher than the static stiffness. • With increasing excitation frequency the stiffness increases, however, this effect is non-linear and varies between 3.7% at high pressure in the narrow tyre and up to 20% at low pressure in the balloon tyre. • Similarly, there is a trend to higher stiffness with increasing vertical load in a magnitude of 20% increase.
Microscopic simulation is an established tool in traffic engineering and research, where aggregated traffic performance measures are inferred from the simulation of individual agents. Additionally, measures describing the safety and efficiency of road user interactions gain importance for recent developments such as automated vehicles and urban cycling. However, current simulation frameworks model interactions including cyclists only with limited realism. To address this issue, we propose to bring bicycle dynamics to traffic simulation. We demonstrate that a novel reformulation of the social force framework can create input signals for a controlled inverted pendulum bicycle model and thereby enable a fully two-dimensional open space simulation of cyclist interactions. The inverted pendulum model introduces the need to stabilize the bicycle as a constraint to the reactive behavior of simulated cyclists. Furthermore, it enables the simulation of countersteering and weaving for stabilization. Our cyclist social forces have anisotropic force fields with respect to relative interaction position and orientation to describe the varying interaction constellations in open space. With these models, we simulate five single- and multi-cyclist test cases and show that the generated trajectories notably differ from results obtained from a 2D bicycle model without lean angle simulation. Measurements of the maximum lateral path deviation and post-encroachment time show that these differences are relevant for typical applications. Our work demonstrates the potential of introducing physics-based realistic bicycle dynamics to the microscopic simulation of individual road user interactions and the fundamental capability of our reformulated cyclist social forces to do so. Going further, we plan to calibrate and validate our model based on naturalistic cycling data to support the initial results of this work.
Since the concept of a Personal Mobility Vehicle (PMV) that tilts inward while turning is relatively new, there is currently a lack of theoretical considerations regarding the suspension mechanism. Therefore, this study aims to explore the theoretical relationship between suspension geometry and the pitching posture during turning in a PMV with two front wheels and one rear wheel that tilts inward during turns. Our findings suggest that a combination of a front telescopic suspension and a rear full trailing arm (swing arm) suspension is suitable for minimizing both the squatting pitching of the vehicle body during turns and the disturbances caused by changes in tread and tire camber angles during wheel strokes in the upright driving position from a static force balance perspective. From a dynamic perspective, there is no significant concern about pitching occurring even in cases where there may be a delay in active tilt angle tracking (PID) control when using the combination of front telescopic suspension and rear full trailing arm suspension. However, it is essential to note that a large sprung roll moment of inertia can still induce the squatting pitching.